Register a new app in the fleet registry
AI agents use fleet_register to create or update resources in Fleet — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fleet environment.
This tool creates a new application entry in a production management system. While not irreversible (could potentially be unregistered), registration commits a new entity to the fleet infrastructure, affecting deployment pipelines, monitoring, and orchestration. The high severity reflects that a malicious actor could register malicious applications or cause confusion in production systems.
From the tool's definition Tool name 'fleet_register' combined with description 'Register a new app in the fleet registry' indicates creation of a new registry entry.
Documented attack patterns abuse exactly the kind of access fleet_register gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fleet, and nothing reaches the server without passing your rules. This is the rule we recommend for fleet_register:
{
"version": "1",
"default": "deny",
"tools": {
"fleet_register": {
"limits": [
{
"counter": "fleet_register_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fleet_register stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Register a new app in the fleet registry. It is categorised as a Write tool in the Fleet MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fleet MCP server in PolicyLayer and add a rule for fleet_register: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Fleet. Nothing to install.
fleet_register is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the fleet_register rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for fleet_register. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
fleet_register is provided by the Fleet MCP server (wrxck/fleet). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Fleet, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
39 Fleet tools catalogued and risk-classified — across an index of 43,000+ MCP servers.